Repeating shotguns used for hunting typically are loaded from the rear barrel and are closed by a longitudinally displaceable chamber. This chamber is relatively long to allow inserting the cartridge and ejecting the cartridge shell. When the firearm is open, collisions with the marksman's head or with the rear stock may arise. Accordingly the firearm as a whole is not easy to handle and its overall length frequently is interfering.
To remedy such drawbacks, long firearms with a fixed barrel haven been supplemented by rifles and smooth bore guns having longitudinally displaceable barrels.
Illustratively such a firearm is known from the German Patent 22 63 378. The barrel resting in sliding manner on a guide rod is fitted at its end with a closing element which engages in geometrically locking manner a closing head that is also supported in longitudinally displaceable manner when the firearm is closed. A locking pin at the closing head will be loosened to open the firearm. Thereupon the barrel is pulled forward by means of the front stock. In the process, two mutually ganged closing rollers will be pivoted to allow disengaging the closing head from the closing element.
This design incurs the drawback that such a mechanism is complex and costly and always requires precise coordination of all closing parts which, in addition to their longitudinal displacements along different axes also must be able to pivot. Accordingly closing the firearm in completely play-free manner is hardly attainable. Manufacture and assembly are elaborate and costly, in substantial part because tight manufacturing tolerances must be observed. Another drawback is that the pivot axes of the closing rollers are situated to the side of the closing head, as a result of which the transmission of force at the instant of firing incurs tipping and torques degrading firing accuracy. Also firearm handling is cumbersome because the barrel must be displaced considerably forward.
Similar conditions apply to a firearm disclosed in U.S. Pat. No. 2,699,006 of which the closing head must also move upward besides carrying out its longitudinal displacement in order to lock the rear barrel end. The closing head, respectively its guide mechanism, is composed of many parts, increasing both manufacturing costs and susceptibility to malfunctioning.
The British patent 756,769 does not use a closing system at the barrel end and instead uses a helical spring permanently pressing the longitudinally displaceable barrel against a stop face within a housing. In order to secure the arm in a closed position and to preclude accidental opening, a pivotably supported locking element engages from the rear a clearance in the barrel sub-assembly. The firing hand removes the locking element out of its detent position to open the firearm. Thereupon the barrel sub-assembly requires being moved forward by means of the front stock against the closing force of the helical spring to allow ejecting the cartridge shell.
As regards a gas-powered automatic firearm disclosed in U.S. Pat. No. 2,628,536, the barrel axially supported in a guide tube also is forced permanently by a helical spring against a stop situated at the housing side and is locked by a locking device configured at the front end of the guide tube. Manual shot repetition at the stop however is problematic with such a firearm because the front stock first must be rotated and then requires being moved forward against the force of the spring. Such a procedure if prolonged not only entails fatigue, but also it requires good coordination and concentration. Moreover the rear barrel end is not closed in geometrically enclosing manner, this feature sometimes being undesirable on safety grounds. Another drawback is the presence of detent recesses in the front region of the barrel. This feature entails higher manufacturing costs and moreover may adversely affect firearm firing. Manufacture is commensurately costly.
U.S. Pat. No. 3,020,662 discloses a repeating shotgun wherein the end of the axially supported barrel is connected by means of a bayonet connection in geometric locking manner to a closing head which is fixed within the housing. To open and close the firearm, the entire barrel must be rotated by means of a laterally offset repeat lever about its axis and be moved forward. Accordingly locking and unlocking the firearm is carried out in the same manner as for a conventional closing chamber, except that the repeat lever, which frequently is interfering, must be moved forward instead of backward.
The objective of the present invention is to eliminate those and further drawbacks of the state of the art and to develop a firearm having a longitudinally displaceable barrel, said firearm being of simple design and easily handled. The entire mechanism inclusive the closing system and the locking system shall be composed of the least number of parts possible that furthermore can be manufactured and assembled in economical manner. The present invention moreover attains in every case force transmission that is free of tipping forces and torques. The firearm always shall function reliably.